The invention relates to vacuum treatment of a waste stream and, more particularly, to vacuum treatment of a waste stream including at least a main processor provided with anti-incrustation measures. Treatment is preferably accomplished by utilization of such processes as and without limitation vacuum and heating processes, mechanical processes, as well as without limitation flash-vapor production and pneumatic-conveyance drying.
Nowadays a particular problem is emerging with what to do with livestock manure from high-density livestock operations. For example, consider the management issues surrounding avian manure. High-rise poultry houses, popular for egg-laying production, are copious producers of avian manure. There are various prior art measures for disposition of the manure, as discussed next. However, these measures are exhausting a particular resource and hence are approaching a kind of obsolescence.
Birds in high-rise chicken houses are kept in multi-story cages typically suspended from ceilings, and their manure is allowed to fall and collect on the floor. These days, disposal usually entails spreading the manure out over agricultural fields as a soil additive. The recently emerging problem with this is that, owners and operators are running out of fields. Historically, owners and operators of high-rise egg-laying houses have also owned a lot of surrounding acreage in fields for this purpose. Not only does this serve as an odor-buffer from the public, but the fields also provide the acreage necessary to accept a given amount of manure that will be spread across it.
To be sure, the manure serves as a wonderful soil additive. However, every field has only a limited capacity to accept so much manure. There becomes a point when too much is too much. Among other constraints on just how much manure the land can accept include those set by governmental oversight for environmental reasons. So, when an owner/operator wants to increase egg-laying capacity, there is a separate consideration that involves identifying additional acreage for spreading out the excess manure.
In other words, if an owner or operator wants to increase egg-producing capacity, constructing additional chicken houses requires not much land. A few dozen acres can support the housing for a truly astounding population of egg-laying hens (millions and millions!). Conversely, the land resource which is easily over-taxed is the acreage available for spreading out the manure. The owner/operators are certainly utilizing all their own nearby landholdings, as well as selling manure at discounted prices to all willing nearby buyers. Of course, the owner/operator can buy more land except that, expense aside, the amount of acreage needed is expansive. It probably won't be on the market. A counterpart solution is to haul excess manure over longer-distances, indeed it ship on a regular schedule to distributed sites, some maybe half way across the nation. At this stage of planning, manure logistics takes on a whole life of its own.
That brings all this to an obstacle. The economics of shipping might overwhelm the economics of simply choosing to build the new high-rise chicken houses at some distantly located site, perhaps halfway across the nation. That way, the new chicken houses can be sited amid an under-served local agricultural-field market for the manure.
What is needed is a solution to the shortcomings of the prior art which can render livestock manure sufficiently lightweight, finely shredded, compact, and substantially deodorized if not pathogen free, so that the logistics of shipping manure cost-compete better against the start-up costs of simply locating new houses at very distant locations.
To turn now to general matters of manure chemistry, manure comprises among other things protein, carbohydrate and fats/oils. Fats/oils and/or the fatty acids they derive from are among the more stable of organic compounds and are not easily decomposed by bacteria or reduced by heat. Indeed, from a cooking perspective, it is common knowledge that proteins and carbohydrates will cook in oils at temperatures which won't cook the oil.
The fats and oils present in manure comprise, not surprisingly, many of the same fats and oils found in livestock and/or their feed. Natural fats and oils are derivatives (or esters to be more accurate) of fatty acids. In general, esters are the products of acids reacted with alcohols or phenols. For example, ethyl alcohol and acetic acid react with the elimination of water to produce ethyl acetate, a volatile liquid with a pleasing fruity odor, and which is used as a solvent especially in lacquers. Animal fats consist mainly of the glyceryl esters of palmitic acid and stearic acid (ie., glyceryl palmitate and glyceryl stearate) and these predominantly form the solid fats. In contrast, glyceryl oleate, the glyceryl ester of oleic acid, is found in olive oil, whale oil and the fats of cold-blooded animals, and it tends to remain liquid at ordinary temperatures.
Fats and oils will be found to convert back to their parent fatty acid under certain circumstances, including by reaction with a mineral acid. However, these parent fatty acids contribute to among other problems the malodorous quality of manure (and along among other things hydrogen sulfide, ammonia, and mercaptans). Formic acid and acetic acid are the first two members of the series of fatty acids (or carboxylic acids to be more accurate). The next two are propionic acid and butyric acid. A hydroxy-propionic acid, lactic acid, is formed for example when milk sours and cabbage ferments. It gives the sour taste to sour milk and sauerkraut. Butyric acid is the principal odorous substance in rancid butter. And so on, with many other of these fatty acids being found in the wastes, by-products and manure of higher life forms. For example, human perspiration includes lactic acid, butyric acid, propionic acid, valeric acid. Chicken manure is known to comprise acetic acid, butyric acid, isobutyric acid, propionic acid and isovaleric acid. The following table gives some physical data for several of the fatty acids.
TABLEacidmelts (° C.)boils (° C.)boils (° F.)acetic17118244propionic−22141285lactic18— (n. 1)—butyric−6164327isobutyric−47154309valeric−35187369oleic14300572palmitic64380716stearic69383721(n. 1): Lactic acid decomposes when heated to 80–100° C. at atmospheric pressure.Linus Paulding, General Chemistry, (Dover Publications, New York), © 1970 Linus Paulding, Table 23-3 (eg., p. 756).
Linus Paulding, General Chemistry, (Dover Publications, New York), © 1970 Linus Paulding, Table 23-3 (eg., p. 756).
It is an object of the invention to crack or otherwise break or explode certain contaminant and/or odorous fractions of manure by flash-vapor production. Flash vapor production is akin to flash steam production. For the foregoing reason, the main processor is operated under a vacuum to enable formation of flash vapors. Consider an example flashing component as if it were water. Water at sea level boils of course at 100° C. (212° F.). However, at ½ an atmosphere (fifteen inches of mercury), water boils at 80° C. (˜180° F.). Indeed as pressure is depressed further, water boils at even lower temperatures still. Hence it is possible to produce flash steam at relatively cool temperatures. Indeed, the lower the vacuum pressure, the more explosive and/or turbulent is the process of flash steam production, which among other things tends to rip the flashing input material to shreds.
The concepts of “flash steam” production and “flash drying” are different concepts despite being denominated with the common term “flash.” Flash drying is a process by which material dries while suspended in a hot pneumatic carrier, as this promotes mixing and efficient heat transfer.
In contrast, the production of “flash steam” is a different phenomenon. When hot water under pressure is released to a lower pressure, part of it is suddenly evaporated, becoming what is known as “flash steam.” The basic physics behind this includes that, when water is heated at atmospheric pressure, its temperature rises until it reaches 100° C. (212° F.), the highest temperature at which water can exist at atmospheric pressure. Additional heat does not raise the temperature, but converts the water to steam. The heat absorbed by the water in raising its temperature to the boiling point is called “sensible heat.” The heat of water at the boiling temperature is called the heat of saturated condensate. Then heat required to convert water at boiling temperature to steam at the same temperature is called “latent heat.”
Note that at pressures lower than atmospheric (eg., vacuum pressures), water boils at relatively lower temperatures. Conversely, the value of latent heat slightly (very slightly) increases with lower pressures although, for practical purposes, the latent heat of water can be considered a constant across pressures between atmospheric and pressure so low that water freezes. So, if saturated water at atmospheric pressure is introduced into a partial vacuum, a certain amount of sensible heat is released. This excess heat will be absorbed in the form of latent heat, causing part of the water to “flash” into steam. To illustrate with real world values, saturated water at atmospheric pressure has a heat content of about 100 kcal/kg (180 Btu/lb). If this condensate is introduced into a ½ atmosphere vacuum, its heat content instantly drops to 82 kcal/kg (147 Btu/lb). The surplus 18 kcal/kg (33 Btu/lb) evaporates or flashes a portion of the condensate into steam. The percentage that will flash to steam can be computed using the formula:% flash stream=[(Sh−Sl)÷H]×100,  (1)where    Sh=Sensible heat in the condensate at the higher pressure before discharge;    Sl=Sensible heat in the condensate at the lower pressure to which discharge takes place; and    H=Latent heat in the steam at the lower pressure to which the condensate has been discharged.
Given that the latent heat of steam for ½ atmosphere is about five-hundred and fifty kcal/kg (one thousand Btu/lb), then the percentage of flash steam computes to about 3⅓ percent.
It is an aspect of the invention to utilize the phenomenon of flash vapor production to promote explosion or shredding of a pre-heated waste stream when introduced into a vacuum processor. The greater the differential in pressure between the pre-heater and the vacuum processor, the better because the activity is more explosive and turbulent, tending to rip the material to shreds as well as otherwise break the molecules of the flashing fractions.
It is a general object of the invention to reduce an input manure stream into a lightweight, finely shredded, compact, and substantially deodorized if not pathogen free output.
A number of additional features and objects will be apparent in connection with the following discussion of preferred embodiments and examples.